Female mammals immunized with proteins of the oocyte zona pellucida (ZP) become infertile, but ovarian dysfunction often occurs. The objectives of this study are to examine the immunogenicity and contraceptive effect of a peptide antigen from the cynomolgus macaque (MCY) ZP and to determine whether immunocontraception with ZP antigens can be dissociated from ovarian dysfunction. A 15-residue segment of the MCY ZP3 protein was synthesized as either a monomer peptide (P1) or as a multiple antigen peptide (8MAP). P1 conjugated to tetanus toxoid (P1-TT) was immunogenic in both mice and NCY. The primary response to 8MAP was weaker. Therefore, 12 female MCY were given a primary immunization consisting of P1-TT and were boosted monthly with 8MAP to avoid hyperimmunity to TT (treated). An additional 12 MCY females were immunized with TT alone and boosted with a tetanus peptide (controls). Although there was considerable variation in the magnitude of the response, all 12 treated MCY developed antibodies against P1, which increased with boosting. No T cell response to P1 has been measured. Profiles of urinary steroid levels and menstrual cycles were unaffected by eight months of immunization. Matings commenced during the fifth month resulting in a conception rate of 36.4% per cycle for the controls and 8.6% per cycle for the treated MCY (p<0.01) in the first two cycles. When boosts were stopped in the eighth month, the treated MCY began to regain fertility. All but 4 have now conceived (12 months). These results support a role for ZP peptides in development of a contraceptive vaccine, but suggest that multiple antigenic epitopes will be required to provide sufficient contraceptive effectiveness. The absence of effects on ovarian function implies that the approach may be safe and reversible. *KEY* Contraceptive, Cynomolgus macaque, Fertility, Menstrual cycle, Ovary, Vaccine